Such a headrest is described in DE 35 19 351 for example. The headrest is vertically adjustable in that a head box that carries the head cushion can be moved relative to the support rods by an electric drive motor. The drive train is provided with an overload safety device in such a way that the drive motor and shafts that drive the head box are rotationally connected by a rotationally elastic coupling. According to a second aspect of the invention, the overload protection consists in that the shafts each have drive wheels that run on a track of the support rod. The drive wheel is designed as a friction wheel.
A headrest that has a support plate fixed to support rods and a plate movable in the X-direction relative to the support plate is described in DE 10 2009 049 946. A guide has rods of the plate and mounted in guide bushes of the support plate. The plate is driven by a shaft provided with two gears each meshing with a toothed rail fixed to the guide rod. A ratchet wheel is fixed to the drive shaft. A latch can be releasably engaged with the ratchet wheel. When the latch is engaged with the ratchet wheel, movement of the plate is blocked.
A headrest that can be vertically adjusted by gear teeth is described in DE 198 00 040, the angle of the headrest section being simultaneously set by the height adjustment.
DE 297 23 240 describes a headrest with which the seat height adjustment is coupled to the headrest height adjustment. When the seat is raised, the headrest adjusts itself downward. When the seat is lowered, the headrest adjusts itself upward. In one embodiment, the headrest height adjustment is driven by a toothed shaft that meshes with gear teeth of the headrest support rods.
A headrest with which a headrest section is mounted for vertical adjustment on support rods is described in DE 10 2004 030 319. Gear teeth that mesh with a drive pinion in order to vertically position the headrest are provided on the support rods. A flexible head cushion is placed over the headrest section and is designed so that it can be changed in shape.